<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <style>
        .c{
            height: 300px;
            width: 500px;
            /*背景色可以输入颜色名称，也可以输入rgb颜色*/
            /*background-color: grey;*/
            background-color: #ff6700;
            /*格式：粗细，实虚，颜色*/
            /*solid：实线*/
            /*dotted:虚线*/
            /*transparent：透明色*/
            /*border: 1px dotted red;*/
            /*只有左边框*/
            border: solid transparent;
        }
        .c:hover {
            border: solid red;
        }

    </style>
</head>
<body>
<div class="c">我是张三</div>
<div class="c1"></div>
</body>
</html>